In the manufacturing process of styrene monomer, to obtain purity, the styrene monomer is distilled. During this distillation step, the thermal reaction causes the formation of styrene oligomer which remains as residue in the still bottoms. The oligomer is a heavy oily viscous liquid and is differentiated from polymer as having an average molecular weight of less than 10.sup.3 (300-750 or 3-8 styrene units). About 2.5% of total styrene monomer distilled forms oligomer, and yearly approximately 150,000,000 lbs are produced. The disposal of these oligomers has produced a serious environmental problem. EPA regulations forbid manufacturers from discharging the bottoms into effluent water streams. Some manufacturers have tried to burn it as a fuel which is highly undesirable as due to its high aromatic content these bottoms produce smoke and peculiarly offensive odor.
It is therefore an object of this invention to provide a method of effectively utilizing these styrene bottoms waste material.
It is another object of this invention to provide a dispersing agent produced from styrene bottoms.
It is yet another object of this invention to provide a salt of sulfonated styrene oligomer.
The foregoing objects and others are accomplished in accordance with this invention by providing a dispersing agent made out of styrene bottoms by sulfonating them and subsequently forming an alkaline salt of it. The advantages of this method will become apparent upon consideration of the following disclosure of the invention.
The dispersing agent of the present invention is prepared as follows:
Styrene still bottoms can be sulfonated either by chlorosulfonic acid or by sulfur trioxide. The sulfonated oligomers are dark brown in color and completely soluble in sodium, potassium, and ammonium hydroxide. Sodium salts of the sulfonated styrene oligomer were prepared as follows: